1. Field of Endeavor
The invention relates to a water separator for steam turbine plants, especially to a preseparator.
2. Brief Description of the Related Art
During the transfer of operating steam from a high-pressure steam turbine into a low-pressure steam turbine, the operating steam is preferably directed through a high-velocity water separator. The separation of water from the operating steam before its reintroduction into the low-pressure steam turbine serves for reducing erosion damage on the turbine blading. In a high-velocity water separator, the separation takes place directly in the transfer pipe, wherein the steam maintains its flow velocity and does not pass through any deviations as a result of complex and large separator components in which the steam velocity is lower.
In the prior art, a distinction is made between preseparators, or water preseparators, and high-velocity water separators, wherein essentially the two achieve a water separation from the operating steam of a turbine while maintaining the high velocity of the steam in the pipe of about 50-70 m/s. A preseparator according to the prior art includes a housing which encloses a crossover, which is designed for separation, from an exhaust steam pipe to a steam transfer pipe. A high-velocity water separator according to the prior art includes a pipe bend in a steam transfer pipe, in which deflecting vanes with openings are arranged, which serve for the discharge of water via the vane interior.
A preseparator is disclosed for example in ABB review 3/1990, pages 3-10, “Operating experiences with new pre- and high-velocity separators”. The exhaust steam from a high-pressure steam turbine flows via an exhaust steam housing into a steam transfer pipe which guides the steam into the low-pressure steam turbine. The preseparator is arranged in a housing which encloses a part of the exhaust steam housing and the starting section of the steam transfer pipe, and has a discharge pipe. The exhaust steam pipe encloses the starting section of the steam transfer pipe, wherein an annular gap exists between the two pipes. A water film, which has been formed from the exhaust steam, flows down along the inside wall of the exhaust steam housing and through the annular gap between the exhaust steam housing and the steam transfer pipe, wherein the discharge of the water is assisted by a steam flow, often also referred to as a transporting steam flow, for the purpose of avoiding a build-up of water at the gap. The water then leaves the separator via the discharge pipe and is fed to a further part of the steam turbine plant. The transporting steam flow is guided via a further steam pipe from the separator and is also fed to a suitable part of the steam turbine plant.
In the same document, a high-velocity water separator is also disclosed which includes a pipe bend in the steam transfer pipe, wherein, on deflecting vanes in the pipe bend, water separation is achieved by openings on the vanes. In this case, a mixture of water and transporting steam flows into the interior of the vanes and is guided into a cavity in which the water is separated from the transporting steam. The water and the transporting steam leave the separator via separate pipes and are fed to further plant components, for example to preheaters.
In both of these separators, the costs of the pipe construction which is necessary for the discharge of transporting steam amount to a significant part of the overall costs of the water separator.
A further high-velocity water separator is known from EP 233 332. The steam transfer pipe again has a pipe bend or a pipe elbow there, in which a number of deflecting vanes are arranged. On the concave side of the deflecting vanes, openings and also associated shrouds are attached, which serve for the discharge of water films which are formed on the vanes. The water in this case is guided via the interior of the vanes into a water discharge pipe, removed from the separator, and fed to a further part of the plant. Transporting steam, which by the deflecting vanes is also entrained through the openings into the interior of the vanes, is fed again to the operating steam in the steam transfer pipe by deflection baffles in the interior of the vanes and by a discharge opening on the convex side of the vanes. A separation of transporting steam and water is achieved in the interior of the vanes as a result.